Process of wood digestion



Patented Aug. 25, 1931 PATENT orl-"lca Harman 3. 312mm, or musxnaon, MICHIGAN,

rnoonss or. woon meas'rron Application a... February 15 1926. Serial No. 88,420.

This invention relates to a process of digesting wood to pulp. It is a primary ob-- ject and purpose of the present invention to procure the proper digestion of wood to pulp f much more rapidly than heretofore, the

time of digestion being very greatly reduced so that a greatly increased production of pulp is obtained. Essentially, the process consists in the simultaneous grinding and digesting of the wood to pulp with a continual agitating of the material so that the digestion liquor is at all times intimately in contact with all'portions of the material being digested.

'An understanding of the invention may be ll/had from the following description taken in connection with the accompanying drawings, in which, Fig. 1 is a longitudinal vertical section through one form of apparatus which may be used to carry out the process, and,

Fig. 2 is a transverse vertical section substantially on the plane of line 2-2 of Fig. 1.

In the construction of the apparatus a cylindrical container 1 is provided having ends 2 closing'the same. At one end of the container-and at its upper side, an inlet at 3 is made forthe admission of the wood chips and digestion liquor into the container. The inlet is adapted to be closed by a bolted and gasketed cover '3a. The finished pulp and the spent or black liquor are withdrawn'from the container through an outlet pipe 4 havinga suitable valve which may be opened or closed b manual operation of the-hand wheel 5. his outlet plpe is at the lower side and opposite end of the apparatus. Steam is admitted to the in rior of the container through a pipe'6 an the pressure within the container is madek own by gauge 7 of conventional construction.

Through each of the ends 2 a sleeveS is passed, the same being rotatably'mounted and a suitable steam, tight packing or stulfing box construction 9 is apgilied to each sleeve to pre vent the escape'o steam or other gaseous materials around the outside of said sleeves. At the inner end'of ea'ch.sleeve a plate 10 is secured having a diameter somewhat less than the interior diameter of the cylinder 1 and a plurality of scraper bars 11 are dis- -high speed.

shaft 25' is eq posed horizontally and at spaced apart intervals between and around the plates 10. These bars are reinforced between their ends by rings 12 located at and att ched to their inner sides. The bars which are 'oved slowly over 5 the-inner surfaces of the container 1 are for the purpose of scraping the pulp from the said surfaces should the same deposit and build upon said surfaces. The use of said bars while very desirable in the apparatus is co- .not absolutely essential.

A" shaft 13 extends through said sleeves 8 the full length of'thecontainer and beyond the outer end ofeach sleeve, there being addi-, tional suitable packings indicated at 14 apo5 plied to the outer. ends of the sleeves to prevent escape of gases around the shaft and between the shaft'and the inne'rsides of the sleeves. Shaft 13 is rotatably supported at each end in suitable bearings at the upper ends .of, posts 15, and atone end the shaft is extended a distance beyond its adj 'acent post .tainamore complete grinding and beating 5 On the shaft 13 between the posts 15 and 15a a pulley 18 is mounted which may be fdri venby a belt 19 from anysuitable source .of power.

The shaft 13 with its attached beating and indingbars 17 is rotated, at

lIearthe'end of shaft 13 a '90 smaller pulley 20 is fixed which, through a belt 21, drivs another pulley 22ffixed to a shaft 231 I The shaft 23 .is associatedwith a reduction gearing. of any suitable form housed within the housing24 so as to drive 'the shaft 25% slow speed. Shaft 25extends the full length of the apparatus andis mounted in suitable bearings in supports 26; The

, ippedwith sprocket wheels 27 in the same plane with which are large 1.00

I shaft 13 an water, there being 1.37

named to each liter sprocket wheels 28 fixed to the sleeves 8. The wheels :28 are driven from the wheels 27 by chains 29,. it being evident that the sleeves 8 and the parts connected therewith move very slowly -com ared to the movement of .the

the arts attached thereto. The material w ich is introduced through the inlet 3 consists of wood chips and the digestion liquor. The digestion liquor is of well known composition including approximately 58% caustic soda, 27% sodium sulfide and 15% sodium carbonate dissolved in ramsof the solids digestion liquid. Steam at one hundred pounds pressure is introduced into the container 1 through the .pipe 6. The rapid rotation of the bars 17 not only continually stirs and agitates the material but the bars striking the same rapidly beat it to a pulp and the digestion liquor permeates the entire mass and 1s brought intimately into. contact with all of the particles of wood chips as they are ground and beaten up by the apparatus. There is a tendency for the pulp to adhere to the inner surface of the cylinder 1 and build up thereon to a certable constituents and chemicals in aqueous solution as commonly used for digestive purposes in a vessel, cutting throu h the said constituents cylindrieally in or er to disintej grate the same and continually heating the digesting liquor and vegetable constituents contained within the said vessel or digestor.

In testimony whereof I aflix m si ature.

HERMAN B. IP ER.

tain depth and this is guarded against by the scraper bars 11 which continually remove any deposit which attempts to adhere to the walls of the container.

The principal advantage of the process out-- lined consists in the rapid digestion of the wood, from one half to three fourths of an 7 hour only being being required to thoroughly digest and reduce to pulp a batch of material placed in the apparatus as against two and one half to three hours required by the regular Kraft digestion process. The digested pulp with the spent or so-called black liquor is discharged through the outlet at 4, the black liquor being recovered from the pulp and reclaimed for future use.

This process is very practical and its commercial utility and advantages are evident from the greatly decreased time that is needed for the digestion of the wood to pulp. Many variations in the form of the apparatus may be resorted to without changingwthe.

process in any essential particular. ile the apparatus is shown as mounted horizontally 1t 15 not confined in any ,sense to horizontal apparatus as vertical apparatus working on the same principles can be employed as well. Accordingly, it is to be understood that the invention is in no sense limited to the particular apparatus used but is directed to the process or method defined in the appended claims.

I-claim: v

1. The herein described process 'of producing cellulose fibres from wood or vegetable matter which consists in placing the said wood or vegetable constituents and chemicals in a ueous solution as commonlyused for digestive purposes in a vessel, con- 

